memory tiers: use default_dram_perf_ref_source in log message

Commit 3718c02 ("acpi, hmat: calculate abstract distance with HMAT")
added a default_dram_perf_ref_source variable that was initialized but
never used.  This causes kmemleak to report the following memory leak:

unreferenced object 0xff11000225a47b60 (size 16):
  comm "swapper/0", pid 1, jiffies 4294761654
  hex dump (first 16 bytes):
    41 43 50 49 20 48 4d 41 54 00 c1 4b 7d b7 75 7c  ACPI HMAT..K}.u|
  backtrace (crc e6d0e7b):
    [<ffffffff95d5afdb>] __kmalloc_node_track_caller_noprof+0x36b/0x440
    [<ffffffff95c276d6>] kstrdup+0x36/0x60
    [<ffffffff95dfabfa>] mt_set_default_dram_perf+0x23a/0x2c0
    [<ffffffff9ad64733>] hmat_init+0x2b3/0x660
    [<ffffffff95203cec>] do_one_initcall+0x11c/0x5c0
    [<ffffffff9ac9cfc4>] do_initcalls+0x1b4/0x1f0
    [<ffffffff9ac9d52e>] kernel_init_freeable+0x4ae/0x520
    [<ffffffff97c789cc>] kernel_init+0x1c/0x150
    [<ffffffff952aecd1>] ret_from_fork+0x31/0x70
    [<ffffffff9520b18a>] ret_from_fork_asm+0x1a/0x30

This reminds us that we forget to use the performance data source
information.  So, use the variable in the error log message to help
identify the root cause of inconsistent performance number.

Link: https://lkml.kernel.org/r/87y13mvo0n.fsf@yhuang6-desk2.ccr.corp.intel.com
Fixes: 3718c02 ("acpi, hmat: calculate abstract distance with HMAT")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reported-by: Waiman Long <longman@redhat.com>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memory-tiers.c

@@ -768,10 +768,10 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
 		pr_info(
 "memory-tiers: the performance of DRAM node %d mismatches that of the reference\n"
 "DRAM node %d.\n", nid, default_dram_perf_ref_nid);
-		pr_info("  performance of reference DRAM node %d:\n",
-			default_dram_perf_ref_nid);
+		pr_info("  performance of reference DRAM node %d from %s:\n",
+			default_dram_perf_ref_nid, default_dram_perf_ref_source);
 		dump_hmem_attrs(&default_dram_perf, "    ");
-		pr_info("  performance of DRAM node %d:\n", nid);
+		pr_info("  performance of DRAM node %d from %s:\n", nid, source);
 		dump_hmem_attrs(perf, "    ");
 		pr_info(
 "  disable default DRAM node performance based abstract distance algorithm.\n");